An earthquake refers to a sudden movement of the earth's interior caused by the release of stress accumulated along geologic faults or by volcanic activity. The earthquake may includes various quakes of the earth's interior, such as microseismic events caused by industrial activities, dynamite explosions used in petroleum and natural gas exploration, small or large natural earthquakes, and nuclear explosions.
When an earthquake takes place, its waves are recorded by seismic stations (more specific, earthquake recording instruments), we want to infer and report its location, magnitude, and source focal mechanism as fast as possible. Current state-of-the-art technology in this area can detect an earthquake's location shortly after the occurrence of the earthquake using P- and/or S-wave travel time information, but the source focal mechanism has to be analyzed and becomes available in hours or days after the earthquake. Current technology for locating earthquakes and reporting earthquake magnitude also often requires a certain level of expertise to infer and ensure estimation accuracy. In the case of magnitude 9.1 earthquake occurring on Dec. 26, 2004 off the west coast of Northern Sumatra, it was not reported timely because of holidays. As a result, warning of tsunami was not issued timely, which led to severe damages and injuries. Reporting focal mechanism of an earthquake in real time is important. For example, Bouchon, M., Karabulut, H., Aktar, M., Ozalaybey, S., Schmittbuhl, J., and Bouin, M-P. (2011). Extended nucleation of the 1999 Mw 7.6 Izmit Earthquake, Sciences 331, 877-88 analyzed the extended nucleation of the 1999 Mw 7.6 Izmit earthquake and found a sequence of foreshocks whose focal mechanisms indicating similar fault slips before accelerating to dynamic rupture. Obtaining foreshock focal mechanisms in real time may help to develop early warning system or even predict earthquakes. However, deriving earthquake focal mechanism requires efforts such as waveform modeling and inversions, which are usually performed in the following hours or days after earthquakes, and it often requires advanced modeling and computational efforts.
A method for rapid determination of source parameters of an earthquake is desired.